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ARS Home » Research » Publications at this Location » Publication #188516
Title: ANALYSIS AND MODELING OF GAS EXCHANGE PROCESSES IN SCAEVOLA AEMULA

Author
item KIM, SOO HYUNG
item FISHER, PAUL - UNIV OF NEW HAMPSHIRE
item LIETH, HEINER - UNIV OF CALIF, DAVIS

Submitted to: Scientia Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/5/2007
Publication Date: 11/1/2007
Citation: Kim, S., Fisher, P.R., Lieth, H. 2007. Analysis and modeling of gas exchange processes in scaevola aemula. Scientia Horticultureae. 114:170-176.

Interpretive Summary: Production of vegetative cuttings of bedding plants is limited by light availability via limited photosynthesis in the greenhouse particularly in the northern regions. Supplemental lightings and CO2 enrichment are complementary technologies often used to boost the production of bedding plants in the greenhouse in such conditions. Experimental investigations of the effects of supplemental lightings, CO2 enrichment, and other environmental controls on greenhouse crop production can be time and resource consuming. On the other hand, crop simulation models can be a useful tool to identify optimal environmental conditions for crop production without extensive experimental investigations. Here, we determined the effects of light, temperature, and CO2 on photosynthesis and transpiration of Scaevola aemula (a.k.a., Australian fan flower), a popular ornamental species widely used as bedding plants or for hanging basket. We then extended a mechanistic simulation model of photosynthesis and transpiration previously developed for cut-roses to this species. The resulting model was capable of simulating photosynthesis and transpiration of Scaevola aemula under various environmental conditions. This model was used to demonstrate the efficacy of CO2 enrichment on production and water use of Scaevola aemula in the greenhouse. The outcome of this research can be applied to assist greenhouse growers for optimizing the greenhouse environment for Scaevola aemula and other bedding plants production.

Technical Abstract: Scaevola aemula is a popular ornamental crop cultivated as a bedding plant or for hanging baskets. We characterized gas exchange properties of S.aemula 'New Wonder' in response to photo synthetically active radiation (PAR), carbon dioxide concentration, and leaf temperature. Net CO2 assimilation rate (A) was responsive to CO2 exhibiting a saturation when intercellular CO2 concentration (Ci) was greater than 600 µmol mol-1. A and dark respiration rate (Rd) were 23.1 and 2.3 µmol m-2 s-1, respectively, at 25 °C and PAR = 1500 µmol m-2 s-1. A was similar between 20 and 30 °C of leaf temperature but was significantly reduced at 15 °C. These gas exchange results were used to test extendibility of a coupled gas exchange model previously developed for cut-roses. Utilizing the gas exchange data measured at 25 °C of leaf temperature, several model parameters were independently determined for S.aemula. Model predictions were then compared with observations at different leaf temperatures. The model predicted the rates of net CO2 assimilation and transpiration of S.aemula reasonably well. Without additional calibration, the model was capable of predicting the temperature dependence of net CO2 assimilation and transpiration rates. Applying the model to predict the effects of CO2 enrichment on photosynthesis and transpiration rates, we show that this model could be a useful tool for examining environmental control options for Scaevola aemula production in the greenhouse.